1. Field of the Invention
This invention relates generally to outdoor area irrigation systems, and more particularly to apparatus for prevention of freezing of water in exposed components.
2. Description of the Prior Art
In communities where water for outdoor irrigation systems for lawns and gardens and the like are supplied by a public or private water utility, governmental codes or ordinances typically require, at the user site, a backflow preventer at the connection from the utility supply to the user's system. The purpose is to prevent flow of contaminated water backward from the user system into the potable water system of the utility due to back-siphoning conditions.
One type of backflow prevention apparatus widely used in lawn irrigation systems is a pressure vacuum breaker valve assembly mounted above ground very close to the water meter and between the water outlet from the meter and the inlet to the irrigation system. During the fall of the year, when ambient temperatures are dropping, it sometimes happens that there is an unseasonable and unusually sharp drop in ambient temperature below the freezing mark. The ground is still warm so there is virtually no danger of water freezing in the underground pipes. However, the backflow preventer valve assembly and the pipes leading to and from it, are above ground.
While it is customary to drain lawn irrigation systems during the fall of the year in the colder climates, it often happens that the owner or manager of the property on which the irrigation system is installed, wants irrigation to continue until a time well into the fall of the year, to maintain the appearance of the property. So, the draining of the system may be delayed until a sudden drop in ambient temperature is predicted. The owner, manager or irrigation service provider frequently does not have the time to drain all of the systems before the temperature drops below freezing. Therefore, the above ground pipes to and from the backflow preventer valve, and which are still pressurized, have water in them which is subjected to the freezing temperatures and can freeze, resulting in breakage of the valve assembly and associated above-ground piping, and significant loss of water (particularly where the property is unattended) when the temperature rises again to normal ambient for that time of the year. The result is significant cost for repair and wasted water, and possible water damage.
Various insulating devices to prevent freezing pipes and hose bibs have been devised. The closest one of which I am aware for a backflow prevention water valve is shown in U.S. Pat. No. Des. 349,754. Irrigation systems are of various sizes and capacities, depending on the area to be irrigated and the available water supply pressures and volume. Therefore, the backflow preventer apparatus also is available in various sizes and types, to accommodate the overall system. In addition, the terrain is not always level, and the surface at the location of the preventer apparatus may be irregular.
It is an object of the present invention to provide a device for reducing the risk of freezing of water in backflow prevention apparatus subjected to transient below-freezing ambient temperatures.